Lion Air? Yes. Ethiopian? No.
Ok, I don't know either but it matches similar information I found elsewhere since my previous post. Point for you. And next, what elaw said applies:
"We are in manual flight, it trims down by iself. I trim up and it stops, but shortly thereafter it trims down by itself again, I trim up... and so on and on, it repeats all the time, and I am finding it harder and harder to keep the nose from going down, but hey, it is not continuous, so let's not cut the trim off and by the way let's also stop trimming up".
If the yoke becomes heavy and you need to pull back on it with increasing force, an OBVIOUS AND NATURAL reaction is to apply nose-up trim.
The stickshaker can be way more confusing though. I am about to stall?
Plus, the noisy trim wheel spinning forward is a clue that is hard to miss.
Is trimming nose-up an obvious and natural response to stickshaker?
Could the noise of the stickshaker mask the noise of the trim wheel?
Right you are, but my demands will apparently go unheeded, so, given only two AoA vanes, we need to establish that the failure of one will not cause a deviation of the flight path = fail-passive.
No, but at least in Lion Air the stickshaker was shaking since rotation when the MCAS would not act because flaps are not retracted. By when they retracted flaps they better had already established that the stall warning was a false one, wither we have to kill the pilots for retracting the flaps and slats in a stall situation.
I don't think so but even if yes, it would be very hard to miss these big black and white wheels spinning.
I still believe that you can achieve that with 2 vanes and 2 sensorless (one based on the left heading, inertial and air data, and the other one based on the right). 2 agreeing vanes would always win ni matter what the sensorless say. In case of vanes disagree, you use the sensorless to monitor the vanes. If at least one of the sensorless agrees with one of the vanes but not with the other, you take that vane as good. In the same way that 2 monitored APs can be used for fail-operational autoland, you don't need 3. If the vanes disagree and no sensorless agrees with any vane, or if one sensorless agrees with one vane and the other one agrees with the other vane, then you are fail-passive. But what are the chances of that? And even then, in the worst case you are fail passive.
Not that I have hopes that Boeing will go into that if they can get rid of it without. It would be a major certification effort.
it would be very hard to miss these big black and white wheels spinning.
That sounds pretty black and white. (sorry)
I don't understand how these sensorless things work, but it seems sooooooo much more complicated than simply adding a third vane. Maybe not. But I think that is moot because I think the FAA is going to let them get away with fail-safe: if the vanes disagree, the system goes inop. This needs to be addressed. I can definitely foresee a rare but plausible scenario in which a faulty sensor becomes a contributing factor and a lack of MCAS protection becomes another factor in a stall-induced accident. The solution here cannot be to lose the artificial stability from a single point of failure.
You owe me a keyboard.
I don't understand how these sensorless things work, but it seems sooooooo much more complicated than simply adding a third vane. Maybe not.
It already exists (for GA) and it is code. No hardware, no cabling, no holes...
But I think that is moot because I think the FAA is going to let them get away with fail-safe
Yes, but will EASA, Canadians, Japanese, Chinese and the airlines follow through?
I don't understand how these sensorless things work
I don't fully understand it wither, but here is the patent pending for it.
https://patents.google.com/patent/US20160298985A1/en
Just to be argumentative, Lion Air seemed to be going so good and then botched it.
Ethiopian took off into all hell and didn't get particularly stabilized with some terrain challenges. (Yes, apparently they didn't get the memo, nor consult the helpful neighborhood, aviation parlour-talk forum.)
I agree. My point was regarding the likelihood of this situation causing more confusion.
Lion Air didn't know what was going on. They did know they had an issue but they seem to be managing it relatively well at first cancelling and counteracting the trim uncommanded inputs with thumb-switch trim. Apparently when the control was transferred to the other pilot, there was no warning from the first one about what he was doing and the second pilot just let the uncommanded trim win. The confusion won.
Now, we don't know yest exactly what happened in the Ethiopian crash. But... Flaps go up and I start getting uncommanded trim down then it stops (be it by itself or after using the thumb switch) and a few seconds later the uncommanded trim down restarts? Then if the had just been reading this forum the immediate response should have been "MCAS, kill the trim". In this scenario, if the stall warning was active since rotation (like in the Lion Air crash) then they evidently judged it false too, since they retracted the flaps (otherwise the MCAS would not have kicked in), so if they were familiar with the details of Lion Air the stall warning should have been an element of clarity, not confusion, by when the MCAS kicked in.
(Yes, apparently they didn't get the memo.)
CNN is reporting that, according to 'a source', they did get the memo and acted on it, but crashed anyway.
https://www.cnn.com/2019/04/03/afric...ntl/index.html
This has to be some CNN nonsense. No one has seen the MCAS schematic (pilots included) but I doubt it involves a dedicated power source to the trim motor. Or does the procedure have to include pulling CB's?
The way I read that article, the pilots followed the procedure for an AoA disagree, which I'm going to speculate does not include disabling the electric trim system.
Another way to read it: in the first paragraph it says the pilots "...initially followed emergency procedures...". The use of the word "initially" says to me they may not have completed the procedure. The first step in the runaway trim procedure is to turn off the autopilot, which in the case of an MCAS problem would not solve the problem. If they stopped at that point in the procedure, the trim would have continued its bad behavior.
More details from Leeham: https://leehamnews.com/2019/04/03/et...-to-stop-mcas/
Apparently they will upload a simulation by Mentour.
Judging by they small part of the WSJ article that is visible until the paywall, the way you should read the article is, they turned off MCAS using Boeing's procedure. Though this is not fully confirmed yet.
Originally posted by Leeham article
The video shows how the slightest miss-trim at Cut-Out creates so high forces on the Stabilator trim jackscrew that a manual turning of the screw via the cables from the trim wheels in the cockpit is no longer possible.
If that's true, that's huge.
flashcrash
No one has seen the MCAS schematic (pilots included) but I doubt it involves a dedicated power source to the trim motor. Or does the procedure have to include pulling CB's?
As I understand it, the suggestion is that they couldn't correct the elevator trim with manual adjustments after disabling MCAS, so in desperation they re-engaged powered trim to help. Worrying if true.